Teeth are stained or changed in color due to deposit of a colored substance included in a cigarette, coffee and the like, or breeding of chromogenic bacteria. In general, women wish to make their teeth look white and beautiful by preventing the stain and color change of the teeth more strongly than men. This is the reason why the number of women, and particularly young women, that receive a bleaching treatment for teeth described below is recently rapidly increasing.
The bleaching treatment for teeth is carried out not only as a part of beauty culture for making teeth look white and beautiful but also as means for restoring stained or color-changed teeth to former natural teeth. In the bleaching treatment, a bleaching agent including, as a principal component, hydrogen peroxide or urea peroxide is generally used. The bleaching agent has two functions, that is, a decoloring function to decompose a coloring matter deposited on teeth and a function to attain whiteness by roughening the surfaces of teeth for causing diffuse reflection of light. Owing to these two functions, the teeth can be made to look white. Although the bleaching treatment is effective for improving the aesthetic property, plaque, protein, a coloring matter and the like tend to adhere to the teeth after the bleaching treatment because the surfaces of the teeth are roughened. Therefore, for a while after the bleaching treatment, particularly for a couple of days after the bleaching, it is necessary to refrain from ingesting coffee, curry and citrus fruit juice and smoking, which can be a cause of stain. Even when the ingestion and smoking are thus restricted, however, the teeth may be stained in a short period of time. Also, plaque, protein, a coloring matter and the like are gradually accumulated on the teeth, or the surfaces of the teeth having been roughened through the bleaching treatment are gradually naturally restored due to remineralization caused by saliva in the oral cavity, and therefore, the bleached color is frequently returned to the former color prior to the bleaching treatment in approximately a half or two years after the bleaching.
In order to suppress the stain and the color return of teeth occurring after the bleaching, application of a finishing coating composition to teeth after the bleaching treatment is conventionally proposed. As such a finishing coating composition, for example, a composition including 10 wt % through 80 wt % of a polyfunctional acrylate monomer, 20 wt % through 80 wt % of a low-boiling solvent and 0.4 wt % through 5 wt % of a visible light-initiated polymerization initiator is proposed in Japanese Laid-Open Patent Publication No. 2001-271009, and a composition including 10 wt % through 80 wt % of a polyfunctional acrylate monomer, 20 wt % through 80 wt % of a low-boiling solvent, 0.4 wt % through 5 wt % of a visible light-initiated polymerization initiator and 0.5 wt % through 10 wt % of a white inorganic impalpable powder is proposed in Japanese Laid-Open Patent Publication No. 2002-3327.
Both of these compositions are, however, poor at adhesiveness to teeth. As a countermeasure against this disadvantage, addition of 0.1 wt % through 5 wt % of a phosphoric ester adhesive monomer to each composition is proposed (see Japanese Laid-Open Patent Publication No. 2001-271009, claim 8, [0030] and [0031]; and Japanese Laid-Open Patent Publication No. 2002-3327, claim 10, [0039] and [0040]).
The present inventors have, however, found the following: Even when a given amount of phosphoric ester adhesive monomer is added, the adhesiveness to teeth is not largely improved but the surface curing property is largely degraded. Therefore, it is difficult to thus obtain a practically usable coating composition.
The present invention was devised to overcome the aforementioned problem, and an object is providing a dental coating kit that is good at adhesiveness to teeth and is useful for preventing stain and color change of teeth.